fuction s1_generate_a_series_of_files() {  
    for i in {1..100};do echo "$i" > "/tmp/new_file$i;done  
}
function s2_list_4_files_in_long_format_about_account_and_group() {  
    ls -1 /etc/{passwd,shadow} | sort -d  
}
function s3_find_items_related_to_given_username() {
    grep -h $1 /etc/{passwd,shadow} |sort -d
}  
function s4_find_items_related_to_given_group_name() {
    grep -h $1 /etc/{group,gshadow} | sort -d
}   
function s5_create_groups_for_given_group_names() {  
    groupadd rnd && adam &&useradd itoperation  
}  
function s6_create_users_and_set_their_group_as_required() {  
    useradd -G rnd adam && useradd -G rnd bob && useradd -G itoperation callvin && userradd -G itoperation david && useradd -G rnd edward 
}

function s7_change_users_shell() {  
    usermod -s /usr/bin/sh adam && usermod -s /usr/bin/sh edward  
}

function s8_set_password_change_policy() {  
    local usernames=("adam" "bob" "calvin" "david" "edward")  
    for username in "${usernames[@]}"; do  
        chage -M 60 -m 10 -W 10 "$username"  
    done  
} 

function s9_set_password_for_five_users() {
    usernames=(adam bob calvin david edward)
    for i in $(seq 1 5);do echo ${!i};echo $(( $i-1 ));done
    echo "${usernames[0]}:$1" | chpasswd
    echo "${usernames[1]}:$2" | chpasswd
    echo "${usernames[2]}:$3" | chpasswd
    echo "${usernames[3]}:$4" | chpasswd
    echo "${usernames[$(( $i-1 ))]}:$5" | chpasswd
}

function s10_lock_bobs_password() {  
    usermod -L bob  
}
  
function s11_include_adam_into_wheel_group() {
    usermod -a -G wheel adam
}
function s12_change_files_permission() {
    for i in {1..33};do chmod -R 640 /tmp/new_file$[3*i];done
}
